U.S. patent application number 11/461895 was filed with the patent office on 2007-02-08 for addition curable silicone resin composition for light emitting diode.
This patent application is currently assigned to Shin-Etsu Chemical Co., Ltd.. Invention is credited to Kei Miyoshi, Naoki Yamakawa.
Application Number | 20070032595 11/461895 |
Document ID | / |
Family ID | 37114337 |
Filed Date | 2007-02-08 |
United States Patent
Application |
20070032595 |
Kind Code |
A1 |
Yamakawa; Naoki ; et
al. |
February 8, 2007 |
ADDITION CURABLE SILICONE RESIN COMPOSITION FOR LIGHT EMITTING
DIODE
Abstract
An addition curable silicone resin composition for a light
emitting diode is provided The composition includes an
organopolysiloxane that includes a straight-chain segment
represented by a formula: -(R.sup.1.sub.2SiO).sub.n- wherein,
R.sup.1 is an unsaturated aliphatic bonding-free monovalent
hydrocarbon group, and n is an integer of 1 or greater, and a
resin-like segment consisting of R.sup.2.sub.3SiO.sub.1/2 units
wherein, R.sup.2 is a monovalent hydrocarbon group, an alkoxy
group, or a hydroxyl group, SiO.sub.2 units, and/or
R.sup.2SiO.sub.3/2 units wherein, R.sup.2 is as defined above, in
which at least two of all the R.sup.2 groups are alkenyl groups.
The composition exhibits strong resistance to thermal shock, and is
resistant to cracking even under severe temperature cycling.
Inventors: |
Yamakawa; Naoki;
(Takasaki-shi, JP) ; Miyoshi; Kei; (Annaka-shi,
JP) |
Correspondence
Address: |
C. IRVIN MCCLELLAND;OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
Shin-Etsu Chemical Co.,
Ltd.
Chiyoda-ku
JP
|
Family ID: |
37114337 |
Appl. No.: |
11/461895 |
Filed: |
August 2, 2006 |
Current U.S.
Class: |
524/862 ;
524/861; 525/477 |
Current CPC
Class: |
C08G 77/16 20130101;
C08G 77/44 20130101; C08L 83/00 20130101; C08G 77/20 20130101; C08G
77/12 20130101; C08G 77/14 20130101; C08L 2205/02 20130101; C08G
77/80 20130101; C08L 83/04 20130101; C08L 83/04 20130101; C08G
77/18 20130101; C08L 2205/035 20130101; C08G 77/70 20130101 |
Class at
Publication: |
524/862 ;
524/861; 525/477 |
International
Class: |
C08L 83/04 20060101
C08L083/04; B32B 27/04 20070101 B32B027/04 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 3, 2005 |
JP |
2005-225716 |
Claims
1. An addition curable silicone resin composition for a light
emitting diode, comprising: (A) an organopolysiloxane comprising: a
straight-chain segment represented by a general formula (1):
-(R.sup.1.sub.2SiO).sub.n- tm (1) (wherein, R.sup.1 represents an
unsubstituted or substituted monovalent hydrocarbon group that
contains no unsaturated aliphatic bonds, and n represents an
integer of 1 or greater), and a resin-like segment, consisting of M
units represented by a general formula: R.sup.2.sub.3SiO.sub.1/2
(wherein, R.sup.2 represents an unsubstituted or substituted
monovalent hydrocarbon group, an alkoxy group, or a hydroxyl
group), and at least one member of Q units represented by a
formula: SiO.sub.2, and T units represented by a formula:
R.sup.2SiO.sub.3/2 (wherein, R.sup.2 is as defined above), in which
at least two of all said R.sup.2 groups are alkenyl groups, (B) an
organohydrogenpolysiloxane containing at least two hydrogen atoms
bonded to silicon atoms within each molecule, in sufficient
quantity that a ratio of silicon atom-bonded hydrogen atoms within
said component (B) relative to all silicon atom-bonded alkenyl
groups within said component (A) is within a range from 0.5 to 4.0,
(C) an effective quantity of an addition reaction catalyst, and (D)
an organohydrogenpolysiloxane compound containing an epoxy group
and/or alkoxy group, in sufficient quantity to provide from 0 to 30
parts by mass per 100 parts by mass of a combination of said
component (A) and said component (B).
2. The composition according to claim 1, wherein in said component
(A), said straight-chain segment exists as a diorganopolysiloxane
molecule containing at least two alkenyl groups bonded to silicon
atoms at molecular terminals within each molecule, and said
resin-like segment exists as a silicone resin molecule consisting
of [M units] and [Q units and/or T units].
3. The composition according to claim 1, wherein in said component
(A), said straight-chain segment and said resin-like segment exist
within a single molecule, and form a single organopolysiloxane
molecule.
4. The composition according to claim 1, wherein in said resin-like
segment, a molar ratio of [M units]/[Q units and/or T units] is
within a range from 0.5 to 1.2.
5. The composition according to claim 1, wherein in said component
(A), a proportion of D units represented by a formula:
R.sup.1.sub.2SiO within all siloxane units is within a range from
10 to 80 mol %.
6. The composition according to claim 1, wherein in said component
(A), a quantity of alkenyl groups within said R.sup.2 groups is
within a range from 0.01 to 1.0 mol per 100 g of said component
(A).
7. The composition according to claim 1, wherein 80 mol % or more
of all organic substituent groups bonded to silicon atoms within
said component (A) are methyl groups.
8. The composition according to claim 1, wherein from 0 to 75 mol %
of all organic substituent groups bonded to silicon atoms within
said component (A) are phenyl groups.
9. The composition according to claim 1, wherein a quantity of
hydrogen atoms bonded to silicon atoms within said component (B) is
within a range from 0.001 to 0.02 mol/g.
10. A light emitting diode sealed with a cured product of an
addition curable silicone resin composition according to claim 1.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an addition curable
silicone resin composition for a light emitting diode (LED), and
relates particularly to an addition curable silicone resin material
that yields a cured product which exhibits excellent transparency,
is ideal for protecting light emitting diode elements, altering or
regulating wavelength, or acting as a lens component material, and
exhibits favorable crack resistance even under conditions involving
high temperature/low temperature cycling.
[0003] 2. Description of the Prior Art
[0004] It is well known that when LEDs are activated and lit, a
rapid rise in temperature occurs, subjecting the LED element to a
thermal shock. Accordingly, when an LED element is turned on and
off repeatedly, the LED element is exposed to severe temperature
cycles.
[0005] Epoxy resins are generally used as the sealing materials for
LED elements. However, because epoxy resins have a high elastic
modulus, the bonding wires are subjected to stress and may break as
a result of temperature cycling, and cracks may develop within the
epoxy resin. Furthermore, as a result of the stress applied by the
epoxy resin to the LED chip, there is also a risk of a
deterioration in the light emission efficiency caused by
destruction of the crystal structure of the semiconductor material.
As a countermeasure to these problems, a method that uses a
room-temperature curable silicone rubber as a buffer material,
wherein the exterior of this rubber is then sealed with an epoxy
resin, is now established as an accepted method. However, with this
method, because the epoxy resin does not adhere to the silicone
rubber, temperature cycling leads to peeling at the interface
between the epoxy resin and the silicone rubber, and it is known
that the light extraction efficiency deteriorates dramatically over
time. The use of silicone resins as alternative materials to epoxy
resins has also been proposed (patent references 1, 2 and 3).
Because silicone resins exhibit comparatively superior heat
resistance, weather resistance and color fastness when compared
with epoxy resins, in recent years, LED examples that use silicone
resins, primarily with blue LEDs and white LEDs, have become more
prevalent. However, although these silicone resins have a lower
elastic modulus than epoxy resins, their mechanical properties such
as their flexural strength are inferior, meaning they suffer from a
tendency for cracks to occur as a result of thermal shock generated
during the turning on and off of the LED.
[0006] [Patent Reference 1] JP 11-1619 A
[0007] [Patent Reference 2] US 2002-0161140 A1
[0008] [Patent Reference 3] US 2004-0116640 A1
SUMMARY OF THE INVENTION
[0009] An object of the present invention is to address the
problems outline above, and provide an addition curable silicone
resin composition for a LED that exhibits strong resistance to
thermal shock, and is resistant to cracking even under severe
temperature cycling.
[0010] As a result of intensive research, the inventors of the
present invention discovered that by employing an
organopolysiloxane comprising a straight-chain segment with high
flexibility and a resin-like segment with high rigidity as the base
material of a silicone resin, the above object could be achieved,
and they were thus able to complete the production of an addition
curable silicone resin composition that is ideal as a sealing
material for LED elements.
[0011] In other words, the present invention provides, as a
solution for achieving the above object, an addition curable
silicone resin composition for a light emitting diode, comprising:
[0012] (A) an organopolysiloxane comprising: [0013] a
straight-chain segment represented by a general formula (1):
-(R.sup.1.sub.2SiO).sub.n- (1) (wherein, R.sup.1 represents an
unsubstituted or substituted monovalent hydrocarbon group that
contains no unsaturated aliphatic bonds, and n represents an
integer of 1 or greater), and [0014] a resin-like segment,
consisting of M units represented by a general formula:
R.sup.2.sub.3SiO.sub.1/2 (wherein, R.sup.2 represents an
unsubstituted or substituted monovalent hydrocarbon group, an
alkoxy group, or a hydroxyl group), Q units represented by a
formula: SiO.sub.2, and/or T units represented by a formula:
R.sup.2SiO.sub.3/2 (wherein, R.sup.2 is as defined above), in which
at least two of all the R.sup.2 groups are alkenyl groups, [0015]
(B) an organohydrogenpolysiloxane containing at least two hydrogen
atoms bonded to silicon atoms within each molecule, in a quantity
within a range from 5 to 50 parts by mass per 100 parts by mass of
the organopolysiloxane of the component (A), [0016] (C) an
effective quantity of an addition reaction catalyst, and [0017] (D)
an organohydrogenpolysiloxane compound containing an epoxy group
and/or an alkoxy group, in sufficient quantity to provide from 0 to
30 parts by mass per 100 parts by mass of a combination of said
component (A) and said component (B).
[0018] An addition curable silicone composition of the present
invention yields a cured product that is highly resistant to
thermal shock, exhibits excellent adhesion to metals and plastics,
and also displays excellent transparency. As a result, it is useful
as a material for light emitting diode elements, and other optical
devices or optical components.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] As follows is a more detailed description of the present
invention. In the following description, "Me" represents a methyl
group, and "Vi" represents a vinyl group. Unless stated otherwise,
viscosity values refer to values measured at 23.degree. C. [0020]
(A) Organopolysiloxane
[0021] An organopolysiloxane used as the component (A) comprises a
straight-chain segment and a resin-like segment, as described
above.
[0022] Examples of the resin-like segment include segments
consisting of M units and Q units, segments consisting of M units
and T units, and segments consisting of M units, Q units, and T
units.
[0023] In the organopolysiloxane of the component (A), there are no
restrictions on the configuration in which the straight-chain
segment and the resin-like segment exist, and typical
configurations include (a) configurations in which the two segments
exist within separate molecules, and the component (A) is a mixture
of those different molecules, and (b) configurations in which the
two segments coexist within a single molecule. In addition, a third
configuration (c) comprising a mixture of organopolysiloxane
molecules of type (a) and organopolysiloxane molecules of type (b)
is also possible.
[0024] In the case of type (b), the component may comprise uniform
organopolysiloxane molecules in which the proportions of the two
segments within each molecule are substantially equal, or may
comprise a mixture of many different molecules with differing
proportions of the two segments.
[0025] [Straight-Chain Segment]
[0026] The straight-chain segment is represented by the general
formula (1), and is the soft segment within the organopolysiloxane
of the component (A) responsible for imparting flexibility to the
molecule. The group R.sup.1 in the general formula (1) is an
unsubstituted or substituted monovalent hydrocarbon group that
contains no unsaturated aliphatic bonds, and n is an integer of 1
or greater.
[0027] Examples of the unsubstituted or substituted monovalent
hydrocarbon group that contains no unsaturated aliphatic bonds
represented by R.sup.1 typically include groups of 1 to 12, and
preferably 1 to 9, carbon atoms, and specific examples include
alkyl groups such as a methyl group, ethyl group, propyl group,
isopropyl group, butyl group, isobutyl group, tert-butyl group,
pentyl group, neopentyl group, hexyl group, cyclohexyl group, octyl
group, nonyl group, or decyl group; aryl groups such as a phenyl
group, tolyl group, xylyl group, or naphthyl group; and aralkyl
groups such as a benzyl group, phenylethyl group, or phenylpropyl
group. Of these, a methyl group or ethyl group is preferred.
[0028] n is an integer of 1 or greater, and is preferably an
integer within a range from 2 to 100, and even more preferably from
7 to 60.
[0029] [Resin-like Segment]
[0030] The "resin-like segment" used herein means a segment which
has a three dimensional structure, and which does not contain a
strait-chain siloxane unit (i.e., difunctional siloxane unit) but
comprises at least one branched siloxane unit (i.e., trifunctional
unit and/or tetrafunctional unit) as an essential unit(s). And the
resin-like segment normally consists of M units represented by a
general formula: R.sup.2.sub.3SiO.sub.1/2 (wherein, R.sup.2
represents an unsubstituted or substituted monovalent hydrocarbon
group, an alkoxy group, or a hydroxyl group), and at least one
member of Q units represented by a formula: SiO.sub.2, and T units
represented by a formula: R.sup.2SiO.sub.3/2 (wherein, R.sup.2 is
as defined above), in which at least two of all the R.sup.2 groups
are alkenyl groups, but does not contain D units described
below.
[0031] Examples of the unsubstituted or substituted monovalent
hydrocarbon groups represented by R.sup.2 within this segment
typically include groups of 1 to 12, and preferably 1 to 9, carbon
atoms, and specific examples include alkyl groups such as a methyl
group, ethyl group, propyl group, isopropyl group, butyl group,
isobutyl group, tert-butyl group, pentyl group, neopentyl group,
hexyl group, cyclohexyl group, octyl group, nonyl group, or decyl
group; aryl groups such as a phenyl group, tolyl group, xylyl
group, or naphthyl group; aralkyl groups such as a benzyl group,
phenylethyl group, or phenylpropyl group; and alkenyl groups such
as a vinyl group, allyl group, propenyl group, isopropenyl group,
butenyl group, hexenyl group, cyclohexenyl group, or octenyl group.
At least two of all the R.sup.2 groups must be alkenyl groups, and
the quantity of alkenyl groups within the R.sup.2 groups is
typically within a range from 0.01 to 1.0 mol per 100 g of the
component (A), and preferably from 0.02 to 0.8 mol per 100 g of the
component (A). Vinyl groups and allyl groups are particularly
preferred as the alkenyl groups.
[0032] Furthermore, examples of the alkoxy groups typically include
groups of 1 to 3 carbon atoms, and specific examples include a
methoxy group, ethoxy group, n-propoxy group, or isopropoxy
group.
[0033] The molar ratio of M units/(Q units and/or T units) within
the resin-like segment is preferably within a range from 0.5 to
1.2, and even more preferably from 0.8 to 1.1. If this ratio of M
units/(Q units and/or T units) is too small, then the number of
cross-linking points within the molecule increases, and the thermal
stability of the molecule becomes undesirably poor, whereas if the
ratio is too large, the viscosity increases, causing an undesirable
deterioration in the workability.
[0034] In the organopolysiloxane of the component (A), the ratio
between the straight-chain segment and the resin-like segment is
preferably such that the ratio of the quantity of diorganosiloxane
units that constitute the straight-chain segment (so-called D units
represented by the formula: R.sup.1.sub.2SiO) relative to the total
quantity of siloxane units within the organopolysiloxane is within
a range from 10 to 80 mol %, and even more preferably from 20 to 50
mol %. If this proportion of D units is too small, then the
flexibility of the component (A) deteriorates, making the component
undesirably fragile, whereas if the proportion is too large, then
the hardness of the cured product decreases undesirably.
[0035] As follows are descriptions of representative examples of
the case in which the organopolysiloxane of the component (A)
comprises solely the type (a) configuration, and the case in which
the organopolysiloxane comprises solely the type (b)
configuration.
[0036] [Type (a)]
[0037] In a component (A) of this type, the straight-chain segment
exists as a straight-chain diorganopolysiloxane that contains at
least two alkenyl groups bonded to silicon atoms at the molecular
terminals within each molecule, and the resin-like segment exists
as a separate silicone resin molecule consisting of M units
together with Q units and/or T units. [0038] Diorganopolysiloxane
containing Straight-Chain Segment
[0039] This diorganopolysiloxane is represented by a general
formula (2) shown below: X-(R.sup.1.sub.2SiO).sub.n-1-Si(R.sup.1)X
(2) (wherein, R.sup.1 and n are as defined above in relation to the
general formula (1), and X is an alkenyl group).
[0040] Specific examples of this diorganopolysiloxane include:
[0041] ViMe.sub.2SiO(SiMe.sub.2O).sub.m(SiViMeO).sub.nSiMe.sub.2Vi,
[0042] Me.sub.3SiO(SiMe.sub.2O).sub.m(SiViMeO).sub.nSiMe.sub.3,
[0043] ViMe.sub.2SiO(SiMe.sub.2O).sub.m(SiViMeO).sub.nSiMe.sub.2Vi,
and [0044]
Vi.sub.3SiO(SiMe.sub.2O).sub.m(SiViMeO).sub.nSiMeVi.sub.3 (wherein,
m represents an integer from 0 to 100, and n represents either 0 or
an integer from 1 to 10).
[0045] The viscosity of this diorganopolysiloxane is typically
within a range from 60 to 100,000 mPas, although because a high
viscosity is not particularly favorable from the viewpoint of
workability, viscosity values of 1,000 mPas or less are preferred,
and values of 100 mPas or less are particularly desirable.
[0046] Silicone Resin
[0047] The silicone resin consists of M units, together with Q
units and/or T units, and in such cases, the molar ratio of M
units/(Q units and/or T units) is preferably within a range from
0.5 to 1.2, and even more preferably from 0.9 to 1.1, and the resin
also contains at least two alkenyl groups within each molecule. The
quantity of these alkenyl groups is typically within a range from
0.01 to 1.0 mol/100 g, and is preferably from 0.02 to 0.8 mol/100
g.
[0048] Furthermore, if the molar ratio of M units/(Q units and/or T
units) is too small, then the molecular weight of the silicone
resin becomes overly high, resulting in an overly high viscosity
and poorer workability, and consequently the ratio is preferably
from 0.8 to 1.2, and even more preferably from 0.9 to 1.1.
[0049] If an attempt is made to increase the hardness of a cured
product of a composition of the present invention by increasing the
value of the ratio [resin-like segment/straight-chain segment],
then although the hardness of the cured product of the composition
increases, the cured product becomes more brittle, increasing the
likelihood of cracking, and consequently the weight ratio
[resin-like segment/organopolysiloxane of the component (A)] is
preferably within a range from 0.8 to 0.1, and even more preferably
from 0.5 to 0.2.
[0050] [Type (b)]
[0051] In a component (A) of this type, the straight-chain segment
and the resin-like segment exist within a single molecule, forming
a single organopolysiloxane molecule.
[0052] In this organopolysiloxane molecule, the straight-chain
segment portion has a structure represented by the general formula
(1) shown above. The resin-like segment portion has a structure
consisting of M units, together with Q units and/or T units, as
described above, and preferably also has a composition represented
by an average composition formula (3) shown below:
R.sup.2.sub.pSiO.sub.(4-p)/2 (3) (wherein, R.sup.2 is as defined in
relation to the general formula (2), the quantity of alkenyl groups
within the R.sup.2 groups is typically within a range from 0.01 to
1.0 mol, and preferably from 0.02 to 0.8 mol per 100 g of the
component (A), and p is a positive number that satisfies 1.ltoreq.p
<2).
[0053] The organopolysiloxane of this type (b) is either a liquid
or solid, and in the case of a liquid, preferably has a viscosity
at 23.degree. C. of at least 100 mPas.
[0054] The type (b) organopolysiloxane can be synthesized by
conducting a hydrolysis and polymerization using either
chlorosilanes, or in some cases chlorosilanes and chlorosiloxanes,
as the monomers, which are selected in accordance with the targeted
composition of the organopolysiloxane.
[0055] In other words, the resin-like segment is formed by
hydrolysis and polymerization of a triorganochlorosilane (an M unit
source), together with an organotrichlorosilane (a T unit source)
and/or tetrachlorosilane (a Q unit source), and the straight-chain
segment is formed by hydrolysis of a diorganodichlorosilane (a D
unit source). If only a diorganodichlorosilane is used as the D
unit source, then in many cases the length of the straight-chain
segment will not extend, meaning an effective soft segment cannot
be obtained, and consequently at least a portion of an .alpha.,
.omega.-dichlorodiorganopolysiloxane (such as a material
represented by the formula
Cl(R.sup.1.sub.2SiO).sub.n-1Si(R.sup.1).sub.2Cl (wherein, R.sup.1
is as defined in relation to the general formula (1), and n
represents an integer of 1 or greater, and preferably an integer
from 5 to 20)) is preferably used in combination with the
diorganodichlorosilane.
[0056] In the above description, when a soft segment chain is
introduced, if the combined total of the vinyldiorganochlorosilane
(number of mols)+ the organotrichlorosilane and/or
tetrachlorosilane (number of mols)+R.sup.1.sub.2SiO units (number
of mols) is deemed 100 mol %, then by adding a quantity of
Cl(R.sup.1.sub.2SiO).sub.n-1Si(R.sup.1).sub.2Cl (wherein, n is an
integer of 1 or greater) that corresponds with a proportion for the
R.sup.1.sub.2SiO units (D units) that preferably falls within a
range from 5 to 40 mol %, and even more preferably from 10 to 25
mol % (in other words, if the combined total of D unit sources
derived from the diorganodichlorosilane and the .alpha.,
.omega.-dichlorodiorganopolysiloxane is within a range from 5 to 40
mol %, and even more preferably from 10 to 25 mol %), then a
silicone material with effective crack resistance is obtained. If
the proportion of Me.sub.2SiO units exceeds 40 mol %, then there is
a danger that the hardness of the resulting cured product may be
less than the targeted hardness value.
[0057] The hydrolysis of the chlorosilanes described above is
conducted in an organic solvent such as a mixture of toluene and
water. Following hydrolysis, polymerization proceeds to some degree
via a dehydrochlorination reaction, but this reaction alone does
not raise the polymerization degree sufficiently, meaning the crack
resistance is unsatisfactory. Accordingly, further condensation is
performed under alkali conditions, thereby improving the crack
resistance. Specifically, this alkali condensation may involve
adding a 50% KOH aqueous solution to the post-hydrolysis toluene
solution of the polymer, which has been washed with water to
generate a neutral solution, using a quantity of 0.05 to 0.5 parts
by mass (and preferably from 0.05 to 0.1 parts by mass) of the KOH
aqueous solution per 100 parts by mass of the polymer, and then
heating the resulting mixture and removing the water that is
generated by azeotropic distillation with toluene. Subsequently,
sufficient trimethylchlorosilane is added to provide a 2-fold
equivalence relative to the quantity of KOH added within the 50%
KOH aqueous solution, and neutralization is then achieved by adding
a 20-fold equivalence of potassium acetate.
[0058] A type (b) organopolysiloxane may also be synthesized by
polymerization of an alkoxysilane, but usually the
organopolysiloxanes obtained by this method yield cured products
with inferior crack resistance. Accordingly, chlorosilanes are
preferred as the hydrolysis raw materials.
[0059] In a type (b) organopolysiloxane, the R.sup.2 groups within
the general formula (3) can be set as methyl groups, phenyl groups
or cyclohexyl groups, depending on the refractive index required of
the composition cured product. [0060] (B)
Organohydrogenpolysiloxane
[0061] An organohydrogenpolysiloxane containing at least two
(typically from 2 to 200), and preferably three or more (for
example, from 3 to 100) hydrogen atoms bonded to silicon atoms
(namely, SiH groups) within each molecule is used as the component
(B). The quantity of the hydrogen atoms is preferably within a
range from 0.001 to 0.02 mol/g, and even more preferably from 0.005
to 0.017 mol/g.
[0062] Monovalent groups other than hydrogen atoms bonded to
silicon atoms within the component (B) are typically substituted or
unsubstituted monovalent hydrocarbon groups, and are preferably
methyl groups or phenyl groups. In those cases where a material
with a high refractive index is required following curing of the
composition of the present invention, phenyl groups are
particularly desirable.
[0063] The organohydrogenpolysiloxane of the component (B) can be
represented by an average composition formula (4) shown below:
R.sup.3.sub.aH.sub.bSiO.sub.(4-a-b)/2 (4) (wherein, each R.sup.3
represents, independently, an unsubstituted or substituted
monovalent hydrocarbon group that contains no alkenyl groups, at
least 30 mol % of all R.sup.3 groups are methyl groups, a is a
number that satisfies 0.7.ltoreq.a.ltoreq.2.1, b is a number that
satisfies 0.001.ltoreq.b.ltoreq.1.0, and a+b represents a number
that satisfies 0.8.ltoreq.a+b.ltoreq.3.0).
[0064] The organohydrogenpolysiloxane functions as a cross-linking
agent that undergoes cross-linking with the alkenyl groups of the
component (A) via a hydrosilylation reaction, and also functions as
a reactive diluent that dilutes the composition to a viscosity best
suited to the intended application. The organohydrogenpolysiloxane
must contain at least two, (typically from 2 to 200), and
preferably three or more (for example, from 3 to approximately 100)
hydrogen atoms bonded to silicon atoms (namely, SiH groups) within
each molecule.
[0065] The viscosity at 25.degree. C. of the
organohydrogenpolysiloxane is preferably no more than 1,000 mPas
(typically within a range from 1 to 1,000 mPas), and is even more
preferably from 5 to 200 mPas.
[0066] Furthermore, the quantity of hydrogen atoms bonded to
silicon atoms is preferably within a range from 0.001 to 0.02 mols,
and even more preferably from 0.005 to 0.017 mols, per 1 g of the
component (B).
[0067] Furthermore, if the hydrocarbon groups of R.sup.1 and
R.sup.2 within the component (A) are alkyl groups such as methyl
groups and ethyl groups, then the R.sup.3 groups within the
component (B) are preferably methyl groups, whereas if the R.sup.1
and R.sup.2 groups include phenyl groups, then at least 5 mol %,
and preferably from 20 to 50 mol % of all the R.sup.3 groups are
preferably phenyl groups. If the refractive indices of the
component (A) and the component (B) are significantly different,
then turbidity may develop after mixing, making it impossible to
obtain a transparent composition.
[0068] Specific examples of the organohydrogenpolysiloxane include
1,3,5,7-tetramethylcyclotetrasiloxane,
tris(dimethylhydrogensiloxy)methylsilane,
tris(dimethylhydrogensiloxy)phenylsilane,
methylhydrogencyclopolysiloxane, cyclic copolymers of
methylhydrogensiloxane and dimethylsiloxane,
methylhydrogenpolysiloxane with both molecular chain terminals
blocked with trimethylsiloxy groups, copolymers of dimethylsiloxane
and methylhydrogensiloxane with both terminals blocked with
trimethylsiloxy groups, dimethylpolysiloxane with both terminals
blocked with dimethylhydrogensiloxy groups, copolymers of
dimethylsiloxane and methylhydrogensiloxane with both terminals
blocked with dimethylhydrogensiloxy groups, copolymers of
methylhydrogensiloxane and diphenylsiloxane with both terminals
blocked with trimethylsiloxy groups, copolymers of
methylhydrogensiloxane and methylphenylsiloxane with both terminals
blocked with trimethylsiloxy groups, copolymers of
methylhydrogensiloxane, diphenylsiloxane and dimethylsiloxane with
both terminals blocked with trimethylsiloxy groups, copolymers of
methylhydrogensiloxane, methylphenylsiloxane and dimethylsiloxane
with both terminals blocked with trimethylsiloxy groups, copolymers
of methylhydrogensiloxane and diphenylsiloxane with both terminals
blocked with dimethylhydrogensiloxy groups, copolymers of
methylhydrogensiloxane and methylphenylsiloxane with both terminals
blocked with dimethylhydrogensiloxy groups, copolymers of
methylhydrogensiloxane, dimethylsiloxane and diphenylsiloxane with
both terminals blocked with dimethylhydrogensiloxy groups,
copolymers of methylhydrogensiloxane, dimethylsiloxane and
methylphenylsiloxane with both terminals blocked with
dimethylhydrogensiloxy groups, polymers in which either a portion
of, or all of, the methyl groups in the above compounds are
substituted with other alkyl groups such as ethyl groups or propyl
groups, or halogenated alkyl groups such as 3,3,3-trifluoropropyl
groups, as well as compounds represented by general formulas (5)
and (6) shown below:
R.sup.3.sub.3SiO[SiR.sup.3(H)O].sub.cSiR.sup.3.sub.3 (5) cyclic
[SiR.sup.3(H)O].sub.d (6) (wherein, R.sup.3 is as defined above, c
represents an integer from 2 to 25, and preferably from 2 to 20,
and d represents an integer from 4 to 8), and compounds represented
by the general formulas shown below: ##STR1## (wherein, R.sup.3 is
as defined above, e represents an integer from 5 to 40, f
represents an integer from 5 to 20, and g represents an integer
from 2 to 30).
[0069] Specific examples of the component (B) also include
compounds represented by the structural formulas shown below.
##STR2##
[0070] The blend quantity of the component (B) is preferably
sufficient to generate a molar ratio of hydrogen atoms bonded to
silicon atoms within the component (B) relative to the total
quantity of alkenyl groups bonded to silicon atoms within the
composition that falls within a range from 0.5 to 4.0, and even
more preferably from 0.7 to 2.0, and most preferably from 1.2 to
1.6. However, in those cases where, in addition to the component
(B), other components containing hydrogen atoms bonded to silicon
atoms also exist (such as the optionally added component (D)
described below), the molar ratio of the total number of silicon
atom-bonded hydrogen atoms within the composition relative to the
total quantity of silicon atom-bonded alkenyl groups within the
composition preferably falls within the above range, that is,
within the range from 0.5 to 4.0, and even more preferably from 0.7
to 2.0, and most preferably from 1.2 to 1.6. In those cases where,
in the manner described above, other components with hydrogen atoms
bonded to silicon atoms exist in addition to the component (B), the
proportion of silicon atom-bonded hydrogen atoms derived from the
component (B), relative to the total quantity of silicon
atom-bonded hydrogen atoms across all the components containing
hydrogen atoms bonded to silicon atoms, is preferably at least 60
mol %, and even more preferably 70 mol % or higher. If this molar
ratio of silicon atom-bonded hydrogen atoms relative to silicon
atom-bonded alkenyl groups is too large or too small, then the
cured product becomes more prone to cracking depending on the shape
of the product.
[0071] The component (B) may be used either alone, or in
combinations of two or more different compounds. [0072] (C)
Addition Reaction Catalyst
[0073] Any of the conventional catalysts known to have a catalytic
action in promoting hydrosilylation reactions can be used as the
addition reaction catalyst, and representative examples include
platinum-based, rhodium-based, and palladium-based catalysts.
Generally, chloroplatinic acid or modified products thereof are
used. Because the present invention relates particularly to
electronics applications, a low-chlorine catalyst is preferred, and
the use of catalysts that have been modified using either
divinyltetramethyldisiloxane or divinyldiphenyldimethyldisiloxane
from which the chlorine fraction has been removed is particularly
preferred. The quantity added of the catalyst need only be a
so-called "effective quantity", although there are no particular
restrictions on the quantity. Specifically, considering the cost of
the material, a quantity equivalent to no more than 50 ppm is
typical, and quantities of no more than 20 ppm are particularly
preferred. However, if this quantity is too low, then the
composition becomes prone to curing inhibition effects, and
consequently the quantity is typically at least 2 ppm. [0074]
Component (D)
[0075] The organohydrogenpolysiloxane compound containing an epoxy
group and/or an alkoxy group of the component (D) is added as an
adhesion improver where required, and imparts self-adhesiveness to
the composition of the present invention. In those cases where a
composition of the present invention is used as an LED sealing
material, this component is typically used for improving the
adhesion of the composition to the resin case or metal on which the
LED chip is mounted.
[0076] The organohydrogen compound of the component (D) contains
one or more (typically from 1 to 20, and preferably from 2 to 10)
hydrogen atoms bonded to silicon atoms (SiH groups), and also
contains organic groups containing an alkoxy group bonded to a
silicon atom and/or an epoxy group bonded to a silicon atom. This
organohydrogen compound typically has a straight-chain or cyclic
siloxane structure containing from 2 to 30, and preferably from 4
to 20, silicon atoms.
[0077] Examples of the alkoxy group include a methoxy group, ethoxy
group, propoxy group, isopropoxy group, butoxy group, sec-butoxy
group, or tert-butoxy group, and this alkoxy group may be either
bonded to a silicon atom that constitutes a siloxane structure
(Si--O--Si), or may be parts of an alkoxysilyl group in which the
alkoxy group is bonded to a silicon atom that constitutes a
siloxane structure via an alkylene group. Furthermore, the epoxy
group-containing organic group is a group in which the epoxy group
is bonded to a silicon atom via a hydrocarbon group (that may also
include an ether linkage oxygen atom), and suitable examples
include the groups shown below. ##STR3##
[0078] Specific examples of the component (D) include the compounds
shown below. (In the following formulas, Me represents a methyl
group.) ##STR4##
[0079] The blend quantity of the component (D) is preferably within
a range from 0 to 30 parts by mass, and even more preferably from 3
to 15 parts by mass, per 100 parts by mass of the overall component
(A). [0080] Other Components
[0081] In addition to the components (A) through (C) described
above, other components besides the component (D) may also be added
to the composition of the present invention if required. For
example, addition reaction retarders for suppressing the curability
and enhancing the pot life, and addition reaction retardants
containing a straight-chain or cyclic alkenyl group may be added,
provided such addition does not impair the effects of the present
invention.
[0082] Furthermore, inorganic fillers such as fumed silica may also
be added for improving the strength, provided such addition does
not adversely affect the transparency, and if required, other
additives such as wavelength regulators, dyes, pigments, flame
retardants, heat resistance improvers, and antioxidants may also be
added.
[0083] Although there are no particular restrictions on the curing
conditions for the above composition, the curing temperature is
preferably within a range from 100 to 150.degree. C., and heating
is typically conducted for approximately 30 to 180 minutes.
[0084] The cured product obtained on curing the composition of the
present invention preferably exhibits a Shore A hardness of at
least 75 in order to prevent damage caused by external stresses,
and a Shore D hardness value of 40 or greater is even more
desirable.
EXAMPLES
[0085] As follows is a description of specifics of the present
invention based on a series of examples and comparative examples,
although the present invention is in no way limited by these
examples. Unless stated otherwise, "parts" refers to parts by
mass.
Example 1
An Example Using a Type (a) Component (A)
[0086] A 50% xylene solution of a silicone resin formed of siloxane
units represented by the formulas Me.sub.3SiO.sub.1/2,
ViMe.sub.2SiO.sub.1/2 and SiO.sub.4/2, and with a molar ratio of
the combination of the Me.sub.3SiO.sub.1/2 units and
ViMe.sub.2SiO.sub.1/2 units relative to the SiO.sub.2 units of 0.95
was stripped for one hour at 120.degree. C. and 15 mmHg, yielding a
silicone resin (as a 50% by mass xylene solution) in which the
vinyl group content of the resin solid fraction was 0.08 mol/100 g,
and 100 parts of this silicone resin (50% by mass xylene solution)
was then mixed with 50 parts of a dimethylpolysiloxane with both
terminals blocked with vinyl groups and with a viscosity at
23.degree. C. of 60 mPas. The solvent was removed from the
resulting mixture by heating for one hour at 120.degree. C. and 15
mmHg, thereby yielding a base polymer. To 100 parts of this base
polymer were added 3 parts of
tetramethyltetravinylcyclotetrasiloxane, 7 parts of a
methylhydrogensiloxane represented by an average molecular formula
shown below: ##STR5## and 5 parts of an epoxy group-containing
hydrogensiloxane represented by a formula (7) shown below: ##STR6##
and the resulting mixture was stirred until uniform, thereby
yielding a transparent liquid mixture. To this liquid mixture was
added a platinum complex catalyst containing
divinyltetramethyldisiloxane ligands, in sufficient quantity to
provide 10 ppm (on a mass basis) of platinum atoms, and the mixture
was then stirred to generate a uniform composition.
[0087] The composition was cured by heating at 100.degree. C. for
one hour and then at 150.degree. C. for a further one hour,
yielding a colorless, transparent resin cured product.
[0088] Measurement of the Shore A hardness of the cured product
revealed a hardness of 75.
Example 2
An Example Using a Type (a) Component (A)
[0089] With the exception of mixing 25 parts of the aforementioned
dimethylpolysiloxane with 150 parts of the aforementioned silicone
resin (the 50% by mass xylene solution), a composition was prepared
in the same manner as the example 1, and curing of this composition
under the same conditions yielded a colorless, transparent resin
cured product.
[0090] Measurement of the Shore D hardness of this cured product
revealed a hardness of 50.
Example 3
An Example Using a Type (a) Component (A)
[0091] With the exception of mixing 20 parts of the aforementioned
dimethylpolysiloxane with 160 parts of the aforementioned silicone
resin (the 50% by mass xylene solution), a composition was prepared
in the same manner as the example 1, and curing of this composition
under the same conditions yielded a colorless, transparent resin
cured product.
[0092] Measurement of the Shore D hardness of this cured product
revealed a hardness of 59.
Comparative Example 1
An Example Using a Type (a) Component (A)
[0093] With the exception of replacing the 100 parts of the base
polymer, prepared by adding 50 parts of the aforementioned
dimethylpolysiloxane to 100 parts of the aforementioned silicone
resin (the 50% by mass xylene solution), with 100 parts of only the
dimethylpolysiloxane, namely the dimethylpolysiloxane with both
terminals blocked with vinyl groups and with a viscosity at
23.degree. C. of 60 mPas, a composition was prepared in the same
manner as the example 1, and curing of this composition under the
same conditions as the example 1 yielded a colorless, transparent
rubber-like cured product.
[0094] Measurement of the Shore A hardness of this cured product
revealed a hardness of 50.
Comparative Example 2
[0095] 200 parts of the same silicone resin (the 50% by mass xylene
solution) as used in Example 1 was mixed with 17.5 parts by mass of
the aforementioned methylhydrogensiloxane represented by the
formula: Me.sub.3SiO(MeHSiO).sub.11SiMe.sub.3, and the mixture was
stripped for one hour at 120.degree. C. and 15 mmHg, yielding a
base polymer. To 117.5 parts by mass of this base polymer were then
added 3 parts of tetramethyltetravinylcyclotetrasiloxane and 5
parts of the epoxy group-containing hydrogensiloxane represented by
the formula (7), and the resulting mixture was stirred until
uniform, thereby yielding a transparent liquid mixture.
[0096] A catalyst was then added to the liquid mixture in the same
manner as the example 1 to prepare a composition, and the
composition was cured in the same manner as the example 1, yielding
a colorless, transparent resin cured product.
[0097] Measurement of the Shore D hardness of this cured product
revealed a hardness of 61. [0098] Evaluations
[0099] The crack resistance and adhesion of the compositions
obtained in the examples 1 to 3 and the comparative examples 1 and
2 were evaluated using the following methods. The results are shown
in Table 1.
[0100] Method of Testing Crack Resistance of Cured Products
[0101] The crack resistance of the cured products obtained in the
examples and comparative examples was measured using the method
described below. For each of the compositions, a washer with a
diameter of approximately 7 mm was placed inside a 25 g wide-necked
transparent glass bottle, and 5 g of the composition was poured
into the bottle and then cured by heating inside a dryer at
100.degree. C. for one hour and then at 150.degree. C. for a
further one hour. Following removal from the dryer and cooling, the
cured product was subjected to 5 cycles of a thermal shock test in
which each cycle involved [30 minutes standing at -40.degree. C.
.fwdarw.30 minutes standing at 120.degree. C.]. The cured product
was then inspected visually for evidence of cracking. The
evaluation was conducted based on the following criteria.
[0102] O: no cracking had occurred
[0103] .DELTA.: minor cracking occurred near the washer
[0104] x: large cracks occurred
[0105] Method of Testing Adhesion
[0106] The adhesion of the compositions obtained in the examples
and comparative examples was measured using the method described
below.
[0107] Each composition was placed on top of a PPA (polyphthalamide
resin) test piece, and then cured by heating inside a dryer at
100.degree. C. for one hour and then at 150.degree. C. for a
further one hour. The strength of the adhesion of the resulting
cured product to the PPA was measured using a method in which a
razor blade was used to cut through the structure in a direction
perpendicular to the cured product layer and the PPA layer, and a
spatula was then used to scratch the cut cross-sectional surface,
and the adhesion was evaluated based on the following criteria.
[0108] O: adhesion across the entire surface, with no areas of
separation between the cured product and the PPA piece
[0109] .DELTA.: partial separation occurred between the cured
product and the PPA piece
[0110] x: separation occurred between the cured product and the PPA
piece across the entire surface TABLE-US-00001 TABLE 1 Comparative
Comparative Example 1 Example 2 Example 3 example 1 example 2
Component/parts Dimethylpolysiloxane 50 25 20 100 Silicone resin 50
75 80 100 (ViMeSiO).sub.4 3 3 3 3 3 Methylhydrogensiloxane 7 10
15.5 5 17.5 Epoxy group-containing 5 5 5 5 5 hydrogensiloxane Total
SiH groups/total vinyl groups 1.3 1.3 1.3 1.3 1.3 within
composition (molar ratio) Hardness D: Shore D hardness A: 85 D: 50
D: 59 A: 50 D: 61 A: Shore A hardness Crack resistance
.smallcircle. .smallcircle. .DELTA. .smallcircle. (on cooling) x
Adhesion to PPA .smallcircle. .smallcircle. .smallcircle. .DELTA.
.DELTA.
Example 4
An Example Using a Type (b) Component (A)
[0111] Using toluene as a solvent, the monomers
phenyltrichlorosilane, vinyldimethylchlorosilane, and a
dichlorodimethylsiloxane represented by an average composition
formula: Cl(Me.sub.2SiO).sub.17Cl were added to the solvent in a
molar ratio of 55:20:25 (wherein the quantity of the
dichlorodimethylsiloxane was calculated as Me.sub.2SiO units), and
following cohydrolysis, a dehydrochlorination condensation was
allowed to proceed at 150.degree. C. for 30 minutes, yielding a 50%
toluene solution of the non-volatile fraction. 0.05 g of a 50%
aqueous solution of KOH was added per 100 g of solid fraction
within the toluene solution, and following conducting a dehydration
condensation reaction at 100.degree. C., neutralization was
conducted by adding 0.1 g of trimethylchlorosilane and 1.0 g of
potassium acetate. In this manner, and based on the added siloxane
units, a solution of an organopolysiloxane with an average
composition represented by the formula:
(C.sub.6H.sub.5).sub.0.55(CH.sub.2.dbd.CH).sub.0.2(CH.sub.3).sub.0.9SiO.s-
ub.1.08 was obtained. The solvent was removed from the
organopolysiloxane solution by heating at 80.degree. C. and 15 mmHg
for one hour, and to 100 parts of the resulting polymer (which even
when free of solvent, was a liquid silicone resin at 80.degree. C.)
were added 24 parts of a cross-linking agent represented by an
average molecular formula shown below (a quantity sufficient to
yield a ratio (molar ratio) of [total SiH groups/total vinyl
groups] within the composition=1): ##STR7## and 10 parts of an
adhesion-imparting component represented by a formula (8) shown
below, thus yielding a transparent liquid mixture. ##STR8## To this
liquid mixture was added a platinum complex catalyst containing
divinyltetramethyldisiloxane ligands, in sufficient quantity to
provide 10 ppm (on a mass basis) of platinum atoms, and the mixture
was then stirred to generate a uniform composition.
[0112] The composition was cured by heating at 100.degree. C. for
one hour and then at 150.degree. C. for a further one hour, thus
yielding a colorless, transparent resin-like cured product. The
Shore D hardness was measured at 68.
Example 5
An Example Using a Type (b) Component (A)
[0113] With the exception of altering the monomers subjected to
hydrolysis to a mixture of phenyltrichlorosilane,
vinyldimethylchlorosilane, dimethyldichlorosilane, and a
dichlorodimethylpolysiloxane represented by an average composition
formula: Cl(Me.sub.2SiO).sub.17Cl in a molar ratio of
55:20:12.5:12.5 (wherein the quantity of the
dichlorodimethylpolysiloxane was calculated as Me.sub.2SiO units),
a composition was prepared in the same manner as the example 4, and
curing of this composition under the same conditions yielded a
colorless, transparent resin-like cured product. The Shore D
hardness was measured at 64.
Comparative Example 3
[0114] With the exception of not subjecting the 50% by mass toluene
solution obtained following cohydrolysis and dehydrochlorination
condensation to the dehydration condensation using KOH, but rather
immediately subjecting the solution to stripping at 80.degree. C.
and 15 mmHg, a composition was prepared in the same manner as the
example 4, and curing of this composition under the same conditions
yielded a colorless, transparent resin-like cured product. The
Shore D hardness was measured at 58.
Comparative Example 4
[0115] With the exception of altering the monomers subjected to
hydrolysis to a mixture of phenyltrichlorosilane,
vinyldimethylchlorosilane, and dimethyldichlorosilane in a molar
ratio of 55:20:25, a composition was prepared in the same manner as
the example 4, and curing of this composition under the same
conditions yielded a colorless, transparent resin-like cured
product. The Shore D hardness was measured at 60.
Comparative Example 5
[0116] Instead of conducting a cohydrolysis in toluene of the
chlorosilanes and dichlorodimethylsiloxane as in the example 4, 28
g of water was added to 200 g of a mixture of
phenyltrimethoxysilane, vinylmethyldiethoxysilane, and a
dimethylsiloxanediol represented by an average composition formula:
HO(Me.sub.2SiO).sub.17H in a molar ratio of 55:20:25 (wherein the
quantity of the dimethylsiloxanediol was calculated as
dimethylsiloxane units), and a cohydrolysis was then conducted
using 3.4 g of methanesulfonic acid as a catalyst. The thus
obtained polymer toluene solution was then treated in the same
manner as the example 4 from the step of adding the KOH aqueous
solution and conducting a dehydration condensation, thereby
yielding a solution of an organopolysiloxane with an average
composition, based on the added siloxane units, represented by the
formula:
(C.sub.6H.sub.5).sub.0.55(CH.sub.2.dbd.CH).sub.0.2(CH.sub.3).sub.0.9SiO.s-
ub.1.08. Subsequent operations were also conducted in the same
manner as the example 4 to complete preparation of a composition,
and curing of this composition under the same conditions yielded a
colorless, transparent resin-like cured product. The Shore D
hardness was measured at 60. [0117] Evaluations
[0118] The crack resistance and adhesion of the compositions
obtained in the examples 4 and 5, and the comparative examples 3 to
5 were evaluated using the methods described above. The results are
shown in Table 2 and Table 3. TABLE-US-00002 TABLE 2 Comparative
Comparative Example 4 Example 5 example 3 example 4
Phenyltrichlorosilane (mol %) 55 55 55 55 Vinyldimethylchlorosilane
(mol %) 20 20 20 20 Cl(Me.sub.2SiO).sub.17Cl (Me.sub.2SiO units mol
%) 25 12.5 25 Dimethyldichlorosilane (mol %) 12.5 25 Condensation
Yes Yes No Yes Hardness (Shore D) 68 64 58 60 Crack resistance
.largecircle. .largecircle. X (at -40.degree. C.) X (at -40.degree.
C.) Adhesion to PPA .largecircle. .largecircle. .largecircle.
.largecircle.
[0119] TABLE-US-00003 TABLE 3 Comparative example 5
Phenyltrimethoxysilane (mol %) 55 Vinylmethyldiethoxysilane (mol %)
20 HO(Me.sub.2SiO).sub.17H (Me.sub.2SiO units mol %) 25
Condensation Yes Hardness (Shore D) 46 Crack resistance X (at
-40.degree. C.) Adhesion to PPA .largecircle.
[Industrial Applicability]
[0120] An addition curable silicone resin composition of the
present invention is useful as a material for light emitting diode
elements and other optical devices or optical components. In other
words, a cured product of the composition is useful as any of a
variety of optical materials, including optical devices, sealing
materials for optical components, lens materials and display
materials, as well as electronic devices, insulating materials for
electronic components, and coating materials.
[0121] More specifically, the composition can be used favorably as
a material for protecting or sealing light emitting diodes, as an
adhesive for bonding structural components or structural members
such as elements or optical devices that use such elements, either
to one another or to substrates, as a material for altering or
regulating the wavelength of light emitted from light emitting
diode elements, as a structural material for members or components
that require favorable optical transparency such as lenses, or as
an adhesive for such members or components.
* * * * *